CHARGE-CARRIER PHOTOEXCITATION AND 2-WAVE MIXING IN DICHROIC MATERIALS

We give experimental and theoretical evidence that two-wave mixing lig ht amplification in electrooptic and photoconductive materials is dram atically influenced by an anisotropic photoexcitation cross section of mobile charge carriers. An enhancement of the two-wave mixing gain is predicted and an increase of 90% is observed in a dichroic Ni doped K NbO3 crystal in a geometry with large angles between the two wave prop agation directions. The enhancement is possible because in anisotropic materials the photogeneration can lead to higher modulation depths as compared to the depth of light intensity modulation.